My guess is the exposure of UV rays from direct sunlight over time turned the white cabinet yellow.
This indeed looks like sun exposure (note the still white outline as light would have been blocked by the grille plastic).
Yes indeed it does. I just noticed that all of the pictures on the Algonquin's page show them being used in a shaded environment and I'm betting it's for this reason.
Although it does state on the page that they are "Painted with automotive-tough paint and topped with an extremely resilient clear coating of ultraviolet ray inhibitor that prevents sun damage to the speaker"
